Protease-containing liquid aqueous detergents are well-known, especially in the context of laundry washing. A commonly encountered problem in said protease-containing liquid aqueous detergents is the degradation phenomenon by the proteolytic enzyme of second enzymes in the composition, such as lipase, amylase and cellulase, or the protease itself.
As a result, the stability of the second enzyme or the proteolytic enzyme itself upon storage in the product, and its effect on cleaning are thus both impaired.
Boric acid and boronic acids are well-known to reversibly inhibit proteolytic enzymes. This inhibition of proteolytic enzyme by boronic acid is reversible upon dilution, as in wash water.
It has now been found that certain boronic acids, i.e. .alpha.-amino boronic acids are particularly effective reversible protease inhibitors in liquid detergent compositions, so that much lower levels of .alpha.-amino boronic acids are needed, compared to other boronic acids, to achieve the same degree of protease inhibition in liquid detergents.
The compositions thus obtained are therefore more environmentally compatible than compositions comprising other boronic acids, in that less boron is eventually released in the environment.
Also, since very low levels of .alpha.-amino boronic acids are needed for an efficient protease inhibition, this allows to free-up several parts of material in the formulation which are then available for other materials. This aspect is particularly critical in the formulation of highly concentrated liquid detergent compositions. These compositions are also encompassed by the present invention.
A discussion of the inhibition of one proteolytic enzyme, subtilisin, is provided in Philipp, M. and Bender, M. L., "Kinetics of Subtilisin and Thiolsubtilisin", Molecular & Cellular Biochemistry, vol. 51, pp. 5-32 (1983).
Copending European Patent Application Serial No. 90/870212 discloses liquid detergent compositions containing certain bacterial serine proteases and lipases.
U.S. Pat. No. 4,566,985 describes liquid cleaning compositions containing a mixture of enzyme at least one of which is a protease. The composition also contains an effective amount of benzamidine hydrochloride to inhibit the digestive effect on the second enzyme.
In European Application 0 376 705, liquid detergents containing a mixture of lipolytic enzymes and proteolytic enzymes have been claimed. The storage stability of lipolytic enzyme towards these proteolytic enzymes is enhanced by inclusion of a lower aliphatic alcohol or lower carboxylic acid.
In European Patent Application 0 381 262, mixtures of proteolytic snd lipolytic enzymes in a liquid medium have been disclosed. The stability of lipase is claimed to be improved by the addition of boron compound and a polyol.
In copending European Patent Application 91870072.5, liquid detergent compositions comprising a protease and a second enzyme have been disclosed wherein the protease is reversibly inhibited by an aromatic borate ester.
In U.S. patent applications Ser. No. 693,515 and 693,516, liquid detergent compositions comprising a protease and a second enzyme have been disclosed wherein the protease is reversibly inhibited by a boric polyol complex or an aryl boronic acid.
In European Patent Application 0 293 881, peptide boronic acids have been disclosed as reversible inhibitors for trypsin-like serine proteases in a therapeutic application.